A bright and dark field switching device, according to the present invention, comprises a glare-proof filter 31 and a condenser lens 32 for a dark field, a guide mechanism 40, and a switching mechanism 60. The glare-proof filter 31 and the condenser lens 32 for a dark field are arranged on both sides with an optical path L of an illuminating optical system interposed therebetween. The guide mechanism 40 holds the glare-proof filter 31 and the condenser lens 32 for a dark field such that they can be moved to the optical path L and can be returned from the optical path L. The switching mechanism 60 moves the glare-proof filter 31 and the condenser lens 32 for a dark field to the optical path L and returns them from the optical path L. Further, the switching mechanism 60 moves the glare-proof filter 31 together so as to position the same on the optical path L only when returning the condenser lens 32 for a dark field from the optical path L.